A central goal of cognitive neuroscience is to elucidate the neural processes that underlie decision making. Even simple decisions often rely on deliberation that extends in time beyond the immediate sensory environment. Thus, the brain requires mechanisms that allow information to combine over time during the deliberative process. This project aims to exploit a recently developed rat-based model of deliberative decision-making to study the neural process that underlies accumulation of evidence and decision commitment. The Brody lab has been able to train rats to perform the Poisson Clicks Accumulation task, where rats make a decision based on comparing the number of auditory clicks presented on two speakers, one to the left of the rat, the other to its right. It has been shown that rats temporally integrate the sensory evidence provided by the clicks to perform this task. We plan to test the extent to which two candidate areas of the rat brain -- the frontal orienting fields (FOF) and posterior parietal cortex (PPC) -- play a role in sensory evidence-based decision making. To do this, we will reversibly inactivate each area separately while rats perform the Poisson Clicks Accumulation task and measure the effect on performance. We will then test whether neurons in these areas represent quantities related to the accumulation of evidence and decision commitment in their responses by recording neural activity during performance of the task. Finally, we will explore the extent to which these areas play similar or different roles using a network model of the decision process. Fulfillment of the aims of this project would further our understanding of the neural processes that underlie decision making and also develop the rat as a model organism for future studies of these questions. Understanding these brain processes is a key step towards developing targeted, principled treatments for disorders of higher brain function.